Device for producing a glass rod

ABSTRACT

A device for the production of a glass rod is provided. The device has a Danner blowpipe constructed to avoid problems attributed to different heat expansion coefficients of the participating materials. The Danner blowpipe has an outer metal jacket surrounding a ceramic body and defines a supply end and a discharge end of the blowpipe. A clamping plate is provided at both the supply and discharge ends. The clamping plate on the discharge end is rigidly joined with a shaft and engages the outer metal jacket at the discharge end. The clamping plate on the supply end is joined in an axially displaceable manner on the shaft, which is rigidly joined with a pressure plate against displacement in an axial direction. A pressure spring is disposed between the pressure plate and the clamping plate on the supply end to urge the plates away from one another.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns a device for producing a glass rod according tothe so-called Danner process, particularly for producing a glass tube.Devices of the named type are known from a plurality of publications.Reference is made to DE 199 60,211 A1 only by way of example.

2. Description of Related Art

Such a device comprises a pipe, the so-called Danner blowpipe, whichrotates slowly and which is generally found inside a heating muffle.Generally the Danner blowpipe is conical and is inclined by itslongitudinal axis slightly toward the horizontal plane. On one end ofthe blowpipe—the larger end in the case of conical blowpipes—acontinuous stream of molten glass is introduced, which forms a laminartrickling film on the jacket surface of the blowpipe. At the smaller endof the blowpipe, the glass rod is drawn off, either as a solid rod or asa tube. After reversing direction in the horizontal plane, thesolidifying rod passes through a roller conveyor up to a drawing machineconnected downstream. It is then broken down into segments of specificlength.

The glass stream has a temperature of approximately 1300° C. when itarrives on the supply end of the Danner blowpipe and a temperature ofapproximately 1000° C. at the so-called a “drawing bulb”. A coolingprocess thus takes place from the supply end to the discharge end. Thecooling process proceeds by the introduction of heat from the heatingmuffle in controlled manner.

DE 198 03,327 C2 refers to a tube-pulling plant according to Danner forglass tubes. The plant comprises a carrier component of ceramics withmetal coating.

DE 2,112,692 A1 describes a leading body for the production of tubes orrods of glass. Here, a hollow body is supported on a spindle. It isrigidly joined with the spindle on one end and is joined in aspring-displaceable manner on the other end.

SUMMARY OF THE INVENTION

The invention originates from a device with a Danner blowpipe of thenamed type, which is constructed in a particular way. Its peripheralwall is formed of an outer metal jacket as well as a ceramic bodysurrounded by the metal jacket. The metal jacket is predominantlycomprised of special steel.

The heat expansion coefficients of the two materials are known to bevery different. The coefficient of the metal is known to besubstantially higher than that of the ceramic material. Since thetemperature of the melt and thus also the temperature of the blowpipeare different from one case to the next, the different heat expansioncoefficients of the two materials lead to problems of forming stability.This is a disadvantage both for the quality of the product as well asalso for the service life of the entire device.

The object of the invention is to configure a device of the named typein such a way that the named problems which are attributed to differentheat expansion coefficients of the participating materials are avoided.At the same time, the device will be of simple construction andinexpensive to produce.

This object is solved by the features of claim 1.

Devices according to the invention can be successfully used particularlyin the production of glass tubes, and in fact, for any type of glasstubes, for example, brown glass tubes. The device permits a relativedisplacement of the ceramic body and the metal jacket in the axialdirection. Thus a displacement path is made available, which could takeup the differences in expansion.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained on the basis of the drawings. The followingare shown individually therein:

FIG. 1 illustrates the basic principle of a device of the named type inschematic representation.

FIG. 2 shows the Danner blowpipe properly speaking in a partiallycut-away orthogonal projection in an enlarged scale.

DETAILED DESCRIPTION OF THE INVENTION

The device shown in FIG. 1 is used by itself for the shaping. It isconnected to the usual components (not shown), namely the drawingchannel with the drawing path and the drawing machine with theseparating device.

The device shown in FIG. 1 comprises a distributor 10 and a pot 20. Themolten glass is discharged from the pot through a nozzle as a continuousstream and strikes the target tool, namely the inclined rotatingblowpipe 1. The blowpipe 1 and the flowing-out opening from the nozzleare found in an oven 2, which assures a temperature gradient between theflowing-out opening from the nozzle and the second end. A blowing device30 serves for sweeping the inner space of the glass tube to be drawn outwith an overpressure opposite the ambient pressure. The glass is drawnout by the blowpipe and reverses direction in the horizontal plane (notshown here).

The blowpipe 1 shown in FIG. 2 is constructed as follows:

It has a peripheral wall, comprising an outer metal jacket 2 as well asa ceramic body 3. It additionally comprises a shaft 6 with clampingplates 6.1, 6.2.

As is seen, both the metal jacket 2 as well as also the ceramic body 3are of conical configuration. Therefore, the larger end of the cone isthe supply end—thus in the region of the clamping plate 6.1—, whereasthe smaller end is the discharge end—thus in the region of the clampingplate 6.2. The ceramic body 3 has a constant wall thickness over theentire length. This is not absolutely necessary, however. The wallthickness could also increase or decrease toward the small end.

The clamping plate 6.2 is a circular disk. In the region of thedischarge end, the metal jacket 2 is bent off at a specific angle to thelongitudinal axis of the Danner blowpipe, in fact in the direction of anincreasing conicity.

The clamping plate 6.1 is of particular configuration at the supply-sideend: As is seen, it comprises a planar disk 6.1.1 as well as a bent-offpart 6.1.2. Part 6.1.2 opens up toward the discharge end. The ceramicbody 3 is chamfered here in such a way that a bearing surface 3.1 isformed. The bent-off part 6.1.2 of the clamping plate 6.1 has acounter-surface 4.3 complementary to the bearing surface 3.1 on itsinner side. The two surfaces 3.1 and 4.3 are inclined at the same angleto the longitudinal axis of the Danner blowpipe. Together, they thusform a seat.

The jacket 2 has a collar 2.1 on its discharge-side end. This latteradjoins the clamping plate 6.2, either indirectly or directly. Shaft 6and clamping plate 6.2 are joined together in a way that resistsrotation, so that a torque can be introduced into the components of theDanner blowpipe via the shaft 6.

Shaft 6 is guided through clamping plate 6.1 at the supply end, forexample, with the intermediate connection of a slide bearing 6.3, sothat an axial displacement can occur between shaft 6 and clamping plate6.1.

In the present case, an elastic force F acts in the direction of thearrow on the supply-side clamping plate 6.1, by means of pressuresprings 7, which are supported against a pressure plate 4.

Based on this configuration, when an expansion occurs due to an increasein temperature, a displacement path a is provided—see the region of theclamping plate 6.2 on the discharge side. The reasoning behind this isthat the metal jacket 2 does not extend over the entire length of theceramic sheath 3. Rather, the supply-side end of the metal jacket 2 mustbe placed at a certain distance to the bent-off part 6.1.2 of theclamping plate 6.1.

Shaft 6 is mounted in a floating manner on the supply-side end, which isnot shown in more detail here. A torque is introduced at this place.

1. A device for producing a glass rod, comprising: a Danner blowpipehaving a jacket surface defining a supply end and a discharge end; and anozzle for introducing a glass stream onto the jacket surface at thesupply end so that a glass film forms and is taken up at the dischargeend, wherein the Danner blowpipe has an outer metal jacket and a ceramicbody surrounded by the outer metal jacket, a clamping plate is providedat the supply end and a clamping plate is provided at the discharge endso that a displacement path is defined between the clamping plate at thedischarge end and the ceramic body, the clamping plate on the dischargeend is rigidly joined with a shaft and engages the outer metal jacket atthe discharge end and the clamping plate on the supply end is joined inan axially displaceable manner on a supply-side of the shaft, which isrigidly joined with a pressure plate against displacement in an axialdirection, and a pressure spring disposed between the pressure plate andthe clamping plate on the supply end and presses the pressure plate andthe clamping plate away from one another, wherein the outer metal jacketextends from the discharge end only over a part of a length of theceramic body.
 2. The device according to claim 1, wherein the outermetal jacket has a collar at the discharge end that supports theclamping plate at the discharge end.
 3. The device according to claim 1,wherein the outer metal jacket has a conical shape with a larger end anda smaller end, and wherein the larger end is proximate the supply endand the smaller end is proximate the discharge end.
 4. The deviceaccording to claim 1, wherein the Danner blowpipe is inclined at anangle to the horizontal plane.
 5. A blowpipe for producing a grass tube,comprising: a shaft for rotating the blowpipe about an axis, said shafthaving first plate and a second plate; a ceramic body having a first endand a second end, said ceramic body being disposed about said shaft sothat said first end is proximate said first plate and said first end ismovable with respect to said shaft along said axis; a resilient memberurging said first plate and said first end away from one another; and ametallic sleeve having a second end opposite said first end of saidceramic body, said metallic sleeve being disposed about said ceramicbody so that said second end of said metallic sleeve is rotatablyengaged with said second plate and so that a displacement path isprovided between said ceramic body and said second end of said metallicsleeve along said axis, wherein said metallic sleeve extends only over apart of a length of said ceramic body.
 6. The blowpipe as in claim 5,further comprising a slide bearing disposed between said first end andsaid shaft.
 7. The blowpipe as in claim 5, wherein said metallic sleevehas a minimum diameter at said second end.
 8. The blowpipe as in claim7, wherein said metallic sleeve has a conical shape.
 9. The blowpipe asin claim 5, wherein said ceramic body has a constant wall thicknessalong said axis.
 10. The blowpipe as in claim 5, wherein said first endcomprises a chamfer defined on said ceramic body and a clamping plateengaging said chamfer.
 11. The blowpipe as in claim 10, wherein saidclamping plate has a planar portion and a bent portion.
 12. The blowpipeas in claim 11, wherein said planar portion engages said resilientmember so that said resilient member can urge said first plate and saidfirst end away from one another.
 13. The blowpipe as in claim 11,wherein said bent portion engages said chamfer.
 14. A blowpipe forproducing a glass tube, comprising: a shaft for rotating the blowpipeabout an axis, said shaft having first plate and a second plate; aceramic body having a first end and a second end, said ceramic bodybeing disposed about said shaft so that said first end is proximate saidfirst plate and said first end is movable with respect to said shaftalong said axis; a metallic sleeve disposed about said ceramic body sothat said second plate causes said shaft, metallic sleeve, and ceramicbody to rotate together about said axis and so that a displacement pathis provided between said ceramic body and said metallic sleeve alongsaid axis at said second end of said ceramic body; and a slide bearingdisposed between said first end and said shaft.
 15. The blowpipe as inclaim 14, wherein said metallic sleeve and said ceramic body havecomplimentary conical shapes.
 16. The blowpipe as in claim 15, whereinsaid ceramic body has a constant wall thickness along said axis.
 17. Ablowpipe for producing a glass tube, comprising: a shaft for rotatingthe blowpipe about an axis, said shaft having first plate and a secondplate; a ceramic body having a first end and a second end, said ceramicbody being disposed about said shaft so that said first end is proximatesaid first plate and said first end is movable with respect to saidshaft along said axis; a metallic sleeve disposed about said ceramicbody so that said second plate causes said shaft, metallic sleeve, andceramic body to rotate together about said axis and so that adisplacement path is provided between said ceramic body and saidmetallic sleeve along said axis at said second end of said ceramic body;and a resilient member urging said first plate and said first end awayfrom one another.
 18. The blowpipe as in claim 17, wherein said metallicsleeve and said ceramic body have complimentary conical shapes.
 19. Theblowpipe as in claim 18, wherein said ceramic body has a constant wallthickness along said axis.